[PATCH] x86 microcode: microcode driver cleanup.

Clean up microcode update driver and make it more readable.

[akpm@osdl.org: cleanups]
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Tigran Aivazian <tigran@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 255 insertions, 258 deletions

diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
index 3fd9f1e8b093..0cbeb26ac3fb 100644
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -416,6 +416,11 @@ config MICROCODE
           To compile this driver as a module, choose M here: the
           module will be called microcode.
 
+config MICROCODE_OLD_INTERFACE
+        bool
+        depends on MICROCODE
+        default y
+
 config X86_MSR
         tristate "/dev/cpu/*/msr - Model-specific register support"
         help
diff --git a/arch/i386/kernel/microcode.c b/arch/i386/kernel/microcode.c
index 40b44cc0d14b..00bdc3dd693e 100644
--- a/arch/i386/kernel/microcode.c
+++ b/arch/i386/kernel/microcode.c
@@ -2,6 +2,7 @@
  *      Intel CPU Microcode Update Driver for Linux
  *
  *      Copyright (C) 2000-2004 Tigran Aivazian
+ *                    2006      Shaohua Li <shaohua.li@intel.com>
  *
  *      This driver allows to upgrade microcode on Intel processors
  *      belonging to IA-32 family - PentiumPro, Pentium II, 
@@ -91,9 +92,6 @@ MODULE_DESCRIPTION("Intel CPU (IA-32) Microcode Update Driver");
 MODULE_AUTHOR("Tigran Aivazian <tigran@veritas.com>");
 MODULE_LICENSE("GPL");
 
-static int verbose;
-module_param(verbose, int, 0644);
-
 #define MICROCODE_VERSION       "1.14a"
 
 #define DEFAULT_UCODE_DATASIZE  (2000)    /* 2000 bytes */
@@ -120,55 +118,40 @@ static DEFINE_SPINLOCK(microcode_update_lock);
 /* no concurrent ->write()s are allowed on /dev/cpu/microcode */
 static DEFINE_MUTEX(microcode_mutex);
 
-static void __user *user_buffer;        /* user area microcode data buffer */
-static unsigned int user_buffer_size;   /* it's size */
-
-typedef enum mc_error_code {
-        MC_SUCCESS      = 0,
-        MC_IGNORED      = 1,
-        MC_NOTFOUND     = 2,
-        MC_MARKED       = 3,
-        MC_ALLOCATED    = 4,
-} mc_error_code_t;
-
 static struct ucode_cpu_info {
+        int valid;
         unsigned int sig;
-        unsigned int pf, orig_pf;
+        unsigned int pf;
         unsigned int rev;
-        unsigned int cksum;
-        mc_error_code_t err;
         microcode_t *mc;
 } ucode_cpu_info[NR_CPUS];
-                                
-static int microcode_open (struct inode *unused1, struct file *unused2)
-{
-        return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
-}
 
-static void collect_cpu_info (void *unused)
+static void collect_cpu_info(int cpu_num)
 {
-        int cpu_num = smp_processor_id();
         struct cpuinfo_x86 *c = cpu_data + cpu_num;
         struct ucode_cpu_info *uci = ucode_cpu_info + cpu_num;
         unsigned int val[2];
 
-        uci->sig = uci->pf = uci->rev = uci->cksum = 0;
-        uci->err = MC_NOTFOUND; 
+        /* We should bind the task to the CPU */
+        BUG_ON(raw_smp_processor_id() != cpu_num);
+        uci->pf = uci->rev = 0;
         uci->mc = NULL;
+        uci->valid = 1;
 
         if (c->x86_vendor != X86_VENDOR_INTEL || c->x86 < 6 ||
                 cpu_has(c, X86_FEATURE_IA64)) {
-                printk(KERN_ERR "microcode: CPU%d not a capable Intel processor\n", cpu_num);
+                printk(KERN_ERR "microcode: CPU%d not a capable Intel "
+                        "processor\n", cpu_num);
+                uci->valid = 0;
                 return;
-        } else {
-                uci->sig = cpuid_eax(0x00000001);
+        }
 
-                if ((c->x86_model >= 5) || (c->x86 > 6)) {
-                        /* get processor flags from MSR 0x17 */
-                        rdmsr(MSR_IA32_PLATFORM_ID, val[0], val[1]);
-                        uci->pf = 1 << ((val[1] >> 18) & 7);
-                }
-                uci->orig_pf = uci->pf;
+        uci->sig = cpuid_eax(0x00000001);
+
+        if ((c->x86_model >= 5) || (c->x86 > 6)) {
+                /* get processor flags from MSR 0x17 */
+                rdmsr(MSR_IA32_PLATFORM_ID, val[0], val[1]);
+                uci->pf = 1 << ((val[1] >> 18) & 7);
         }
 
         wrmsr(MSR_IA32_UCODE_REV, 0, 0);
@@ -180,218 +163,160 @@ static void collect_cpu_info (void *unused)
                         uci->sig, uci->pf, uci->rev);
 }
 
-static inline void mark_microcode_update (int cpu_num, microcode_header_t *mc_header, int sig, int pf, int cksum)
+static inline int microcode_update_match(int cpu_num,
+        microcode_header_t *mc_header, int sig, int pf)
 {
         struct ucode_cpu_info *uci = ucode_cpu_info + cpu_num;
 
-        pr_debug("Microcode Found.\n");
-        pr_debug("   Header Revision 0x%x\n", mc_header->hdrver);
-        pr_debug("   Loader Revision 0x%x\n", mc_header->ldrver);
-        pr_debug("   Revision 0x%x \n", mc_header->rev);
-        pr_debug("   Date %x/%x/%x\n",
-                ((mc_header->date >> 24 ) & 0xff),
-                ((mc_header->date >> 16 ) & 0xff),
-                (mc_header->date & 0xFFFF));
-        pr_debug("   Signature 0x%x\n", sig);
-        pr_debug("   Type 0x%x Family 0x%x Model 0x%x Stepping 0x%x\n",
-                ((sig >> 12) & 0x3),
-                ((sig >> 8) & 0xf),
-                ((sig >> 4) & 0xf),
-                ((sig & 0xf)));
-        pr_debug("   Processor Flags 0x%x\n", pf);
-        pr_debug("   Checksum 0x%x\n", cksum);
-
-        if (mc_header->rev < uci->rev) {
-                if (uci->err == MC_NOTFOUND) {
-                        uci->err = MC_IGNORED;
-                        uci->cksum = mc_header->rev;
-                } else if (uci->err == MC_IGNORED && uci->cksum < mc_header->rev)
-                        uci->cksum = mc_header->rev;
-        } else if (mc_header->rev == uci->rev) {
-                if (uci->err < MC_MARKED) {
-                        /* notify the caller of success on this cpu */
-                        uci->err = MC_SUCCESS;
-                }
-        } else if (uci->err != MC_ALLOCATED || mc_header->rev > uci->mc->hdr.rev) {
-                pr_debug("microcode: CPU%d found a matching microcode update with "
-                        " revision 0x%x (current=0x%x)\n", cpu_num, mc_header->rev, uci->rev);
-                uci->cksum = cksum;
-                uci->pf = pf; /* keep the original mc pf for cksum calculation */
-                uci->err = MC_MARKED; /* found the match */
-                for_each_online_cpu(cpu_num) {
-                        if (ucode_cpu_info + cpu_num != uci
-                            && ucode_cpu_info[cpu_num].mc == uci->mc) {
-                                uci->mc = NULL;
-                                break;
-                        }
-                }
-                if (uci->mc != NULL) {
-                        vfree(uci->mc);
-                        uci->mc = NULL;
-                }
-        }
-        return;
+        if (!sigmatch(sig, uci->sig, pf, uci->pf)
+                || mc_header->rev <= uci->rev)
+                return 0;
+        return 1;
 }
 
-static int find_matching_ucodes (void) 
+static int microcode_sanity_check(void *mc)
 {
-        int cursor = 0;
-        int error = 0;
-
-        while (cursor + MC_HEADER_SIZE < user_buffer_size) {
-                microcode_header_t mc_header;
-                void *newmc = NULL;
-                int i, sum, cpu_num, allocated_flag, total_size, data_size, ext_table_size;
+        microcode_header_t *mc_header = mc;
+        struct extended_sigtable *ext_header = NULL;
+        struct extended_signature *ext_sig;
+        unsigned long total_size, data_size, ext_table_size;
+        int sum, orig_sum, ext_sigcount = 0, i;
+
+        total_size = get_totalsize(mc_header);
+        data_size = get_datasize(mc_header);
+        if ((data_size + MC_HEADER_SIZE > total_size)
+                || (data_size < DEFAULT_UCODE_DATASIZE)) {
+                printk(KERN_ERR "microcode: error! "
+                        "Bad data size in microcode data file\n");
+                return -EINVAL;
+        }
 
-                if (copy_from_user(&mc_header, user_buffer + cursor, MC_HEADER_SIZE)) {
-                        printk(KERN_ERR "microcode: error! Can not read user data\n");
-                        error = -EFAULT;
-                        goto out;
+        if (mc_header->ldrver != 1 || mc_header->hdrver != 1) {
+                printk(KERN_ERR "microcode: error! "
+                        "Unknown microcode update format\n");
+                return -EINVAL;
+        }
+        ext_table_size = total_size - (MC_HEADER_SIZE + data_size);
+        if (ext_table_size) {
+                if ((ext_table_size < EXT_HEADER_SIZE)
+                 || ((ext_table_size - EXT_HEADER_SIZE) % EXT_SIGNATURE_SIZE)) {
+                        printk(KERN_ERR "microcode: error! "
+                                "Small exttable size in microcode data file\n");
+                        return -EINVAL;
                 }
-
-                total_size = get_totalsize(&mc_header);
-                if ((cursor + total_size > user_buffer_size) || (total_size < DEFAULT_UCODE_TOTALSIZE)) {
-                        printk(KERN_ERR "microcode: error! Bad data in microcode data file\n");
-                        error = -EINVAL;
-                        goto out;
+                ext_header = mc + MC_HEADER_SIZE + data_size;
+                if (ext_table_size != exttable_size(ext_header)) {
+                        printk(KERN_ERR "microcode: error! "
+                                "Bad exttable size in microcode data file\n");
+                        return -EFAULT;
                 }
+                ext_sigcount = ext_header->count;
+        }
 
-                data_size = get_datasize(&mc_header);
-                if ((data_size + MC_HEADER_SIZE > total_size) || (data_size < DEFAULT_UCODE_DATASIZE)) {
-                        printk(KERN_ERR "microcode: error! Bad data in microcode data file\n");
-                        error = -EINVAL;
-                        goto out;
+        /* check extended table checksum */
+        if (ext_table_size) {
+                int ext_table_sum = 0;
+                int * ext_tablep = (int *)ext_header;
+
+                i = ext_table_size / DWSIZE;
+                while (i--)
+                        ext_table_sum += ext_tablep[i];
+                if (ext_table_sum) {
+                        printk(KERN_WARNING "microcode: aborting, "
+                                "bad extended signature table checksum\n");
+                        return -EINVAL;
                 }
+        }
 
-                if (mc_header.ldrver != 1 || mc_header.hdrver != 1) {
-                        printk(KERN_ERR "microcode: error! Unknown microcode update format\n");
-                        error = -EINVAL;
-                        goto out;
+        /* calculate the checksum */
+        orig_sum = 0;
+        i = (MC_HEADER_SIZE + data_size) / DWSIZE;
+        while (i--)
+                orig_sum += ((int *)mc)[i];
+        if (orig_sum) {
+                printk(KERN_ERR "microcode: aborting, bad checksum\n");
+                return -EINVAL;
+        }
+        if (!ext_table_size)
+                return 0;
+        /* check extended signature checksum */
+        for (i = 0; i < ext_sigcount; i++) {
+                ext_sig = (struct extended_signature *)((void *)ext_header
+                        + EXT_HEADER_SIZE + EXT_SIGNATURE_SIZE * i);
+                sum = orig_sum
+                        - (mc_header->sig + mc_header->pf + mc_header->cksum)
+                        + (ext_sig->sig + ext_sig->pf + ext_sig->cksum);
+                if (sum) {
+                        printk(KERN_ERR "microcode: aborting, bad checksum\n");
+                        return -EINVAL;
                 }
+        }
+        return 0;
+}
 
-                for_each_online_cpu(cpu_num) {
-                        struct ucode_cpu_info *uci = ucode_cpu_info + cpu_num;
-
-                        if (sigmatch(mc_header.sig, uci->sig, mc_header.pf, uci->orig_pf))
-                                mark_microcode_update(cpu_num, &mc_header, mc_header.sig, mc_header.pf, mc_header.cksum);
-                }
+/*
+ * return 0 - no update found
+ * return 1 - found update
+ * return < 0 - error
+ */
+static int get_maching_microcode(void *mc, int cpu)
+{
+        struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
+        microcode_header_t *mc_header = mc;
+        struct extended_sigtable *ext_header;
+        unsigned long total_size = get_totalsize(mc_header);
+        int ext_sigcount, i;
+        struct extended_signature *ext_sig;
+        void *new_mc;
+
+        if (microcode_update_match(cpu, mc_header,
+                        mc_header->sig, mc_header->pf))
+                goto find;
+
+        if (total_size <= get_datasize(mc_header) + MC_HEADER_SIZE)
+                return 0;
+
+        ext_header = (struct extended_sigtable *)(mc +
+                        get_datasize(mc_header) + MC_HEADER_SIZE);
+        ext_sigcount = ext_header->count;
+        ext_sig = (struct extended_signature *)((void *)ext_header
+                        + EXT_HEADER_SIZE);
+        for (i = 0; i < ext_sigcount; i++) {
+                if (microcode_update_match(cpu, mc_header,
+                                ext_sig->sig, ext_sig->pf))
+                        goto find;
+                ext_sig++;
+        }
+        return 0;
+find:
+        pr_debug("microcode: CPU %d found a matching microcode update with"
+                " version 0x%x (current=0x%x)\n", cpu, mc_header->rev,uci->rev);
+        new_mc = vmalloc(total_size);
+        if (!new_mc) {
+                printk(KERN_ERR "microcode: error! Can not allocate memory\n");
+                return -ENOMEM;
+        }
 
-                ext_table_size = total_size - (MC_HEADER_SIZE + data_size);
-                if (ext_table_size) {
-                        struct extended_sigtable ext_header;
-                        struct extended_signature ext_sig;
-                        int ext_sigcount;
+        /* free previous update file */
+        vfree(uci->mc);
 
-                        if ((ext_table_size < EXT_HEADER_SIZE) 
-                                        || ((ext_table_size - EXT_HEADER_SIZE) % EXT_SIGNATURE_SIZE)) {
-                                printk(KERN_ERR "microcode: error! Bad data in microcode data file\n");
-                                error = -EINVAL;
-                                goto out;
-                        }
-                        if (copy_from_user(&ext_header, user_buffer + cursor 
-                                        + MC_HEADER_SIZE + data_size, EXT_HEADER_SIZE)) {
-                                printk(KERN_ERR "microcode: error! Can not read user data\n");
-                                error = -EFAULT;
-                                goto out;
-                        }
-                        if (ext_table_size != exttable_size(&ext_header)) {
-                                printk(KERN_ERR "microcode: error! Bad data in microcode data file\n");
-                                error = -EFAULT;
-                                goto out;
-                        }
-
-                        ext_sigcount = ext_header.count;
-                        
-                        for (i = 0; i < ext_sigcount; i++) {
-                                if (copy_from_user(&ext_sig, user_buffer + cursor + MC_HEADER_SIZE + data_size + EXT_HEADER_SIZE 
-                                                + EXT_SIGNATURE_SIZE * i, EXT_SIGNATURE_SIZE)) {
-                                        printk(KERN_ERR "microcode: error! Can not read user data\n");
-                                        error = -EFAULT;
-                                        goto out;
-                                }
-                                for_each_online_cpu(cpu_num) {
-                                        struct ucode_cpu_info *uci = ucode_cpu_info + cpu_num;
-
-                                        if (sigmatch(ext_sig.sig, uci->sig, ext_sig.pf, uci->orig_pf)) {
-                                                mark_microcode_update(cpu_num, &mc_header, ext_sig.sig, ext_sig.pf, ext_sig.cksum);
-                                        }
-                                }
-                        }
-                }
-                /* now check if any cpu has matched */
-                allocated_flag = 0;
-                sum = 0;
-                for_each_online_cpu(cpu_num) {
-                        if (ucode_cpu_info[cpu_num].err == MC_MARKED) { 
-                                struct ucode_cpu_info *uci = ucode_cpu_info + cpu_num;
-                                if (!allocated_flag) {
-                                        allocated_flag = 1;
-                                        newmc = vmalloc(total_size);
-                                        if (!newmc) {
-                                                printk(KERN_ERR "microcode: error! Can not allocate memory\n");
-                                                error = -ENOMEM;
-                                                goto out;
-                                        }
-                                        if (copy_from_user(newmc + MC_HEADER_SIZE, 
-                                                                user_buffer + cursor + MC_HEADER_SIZE, 
-                                                                total_size - MC_HEADER_SIZE)) {
-                                                printk(KERN_ERR "microcode: error! Can not read user data\n");
-                                                vfree(newmc);
-                                                error = -EFAULT;
-                                                goto out;
-                                        }
-                                        memcpy(newmc, &mc_header, MC_HEADER_SIZE);
-                                        /* check extended table checksum */
-                                        if (ext_table_size) {
-                                                int ext_table_sum = 0;
-                                                int * ext_tablep = (((void *) newmc) + MC_HEADER_SIZE + data_size);
-                                                i = ext_table_size / DWSIZE;
-                                                while (i--) ext_table_sum += ext_tablep[i];
-                                                if (ext_table_sum) {
-                                                        printk(KERN_WARNING "microcode: aborting, bad extended signature table checksum\n");
-                                                        vfree(newmc);
-                                                        error = -EINVAL;
-                                                        goto out;
-                                                }
-                                        }
-
-                                        /* calculate the checksum */
-                                        i = (MC_HEADER_SIZE + data_size) / DWSIZE;
-                                        while (i--) sum += ((int *)newmc)[i];
-                                        sum -= (mc_header.sig + mc_header.pf + mc_header.cksum);
-                                }
-                                ucode_cpu_info[cpu_num].mc = newmc;
-                                ucode_cpu_info[cpu_num].err = MC_ALLOCATED; /* mc updated */
-                                if (sum + uci->sig + uci->pf + uci->cksum != 0) {
-                                        printk(KERN_ERR "microcode: CPU%d aborting, bad checksum\n", cpu_num);
-                                        error = -EINVAL;
-                                        goto out;
-                                }
-                        }
-                }
-                cursor += total_size; /* goto the next update patch */
-        } /* end of while */
-out:
-        return error;
+        memcpy(new_mc, mc, total_size);
+        uci->mc = new_mc;
+        return 1;
 }
 
-static void do_update_one (void * unused)
+static void apply_microcode(int cpu)
 {
         unsigned long flags;
         unsigned int val[2];
-        int cpu_num = smp_processor_id();
+        int cpu_num = raw_smp_processor_id();
         struct ucode_cpu_info *uci = ucode_cpu_info + cpu_num;
 
-        if (uci->mc == NULL) {
-                if (verbose) {
-                        if (uci->err == MC_SUCCESS)
-                                printk(KERN_INFO "microcode: CPU%d already at revision 0x%x\n",
-                                        cpu_num, uci->rev);
-                        else
-                                printk(KERN_INFO "microcode: No new microcode data for CPU%d\n", cpu_num);
-                }
+        /* We should bind the task to the CPU */
+        BUG_ON(cpu_num != cpu);
+
+        if (uci->mc == NULL)
                 return;
-        }
 
         /* serialize access to the physical write to MSR 0x79 */
         spin_lock_irqsave(&microcode_update_lock, flags);          
@@ -408,54 +333,98 @@ static void do_update_one (void * unused)
         /* get the current revision from MSR 0x8B */
         rdmsr(MSR_IA32_UCODE_REV, val[0], val[1]);
 
-        /* notify the caller of success on this cpu */
-        uci->err = MC_SUCCESS;
         spin_unlock_irqrestore(&microcode_update_lock, flags);
-        printk(KERN_INFO "microcode: CPU%d updated from revision "
+        if (val[1] != uci->mc->hdr.rev) {
+                printk(KERN_ERR "microcode: CPU%d updated from revision "
+                        "0x%x to 0x%x failed\n", cpu_num, uci->rev, val[1]);
+                return;
+        }
+        pr_debug("microcode: CPU%d updated from revision "
                "0x%x to 0x%x, date = %08x \n", 
                cpu_num, uci->rev, val[1], uci->mc->hdr.date);
-        return;
+        uci->rev = val[1];
 }
 
-static int do_microcode_update (void)
-{
-        int i, error;
+#ifdef CONFIG_MICROCODE_OLD_INTERFACE
+static void __user *user_buffer;        /* user area microcode data buffer */
+static unsigned int user_buffer_size;   /* it's size */
 
-        if (on_each_cpu(collect_cpu_info, NULL, 1, 1) != 0) {
-                printk(KERN_ERR "microcode: Error! Could not run on all processors\n");
-                error = -EIO;
-                goto out;
+static long get_next_ucode(void **mc, long offset)
+{
+        microcode_header_t mc_header;
+        unsigned long total_size;
+
+        /* No more data */
+        if (offset >= user_buffer_size)
+                return 0;
+        if (copy_from_user(&mc_header, user_buffer + offset, MC_HEADER_SIZE)) {
+                printk(KERN_ERR "microcode: error! Can not read user data\n");
+                return -EFAULT;
         }
-
-        if ((error = find_matching_ucodes())) {
-                printk(KERN_ERR "microcode: Error in the microcode data\n");
-                goto out_free;
+        total_size = get_totalsize(&mc_header);
+        if ((offset + total_size > user_buffer_size)
+                || (total_size < DEFAULT_UCODE_TOTALSIZE)) {
+                printk(KERN_ERR "microcode: error! Bad total size in microcode "
+                                "data file\n");
+                return -EINVAL;
         }
-
-        if (on_each_cpu(do_update_one, NULL, 1, 1) != 0) {
-                printk(KERN_ERR "microcode: Error! Could not run on all processors\n");
-                error = -EIO;
+        *mc = vmalloc(total_size);
+        if (!*mc)
+                return -ENOMEM;
+        if (copy_from_user(*mc, user_buffer + offset, total_size)) {
+                printk(KERN_ERR "microcode: error! Can not read user data\n");
+                vfree(*mc);
+                return -EFAULT;
         }
+        return offset + total_size;
+}
 
-out_free:
-        for_each_online_cpu(i) {
-                if (ucode_cpu_info[i].mc) {
-                        int j;
-                        void *tmp = ucode_cpu_info[i].mc;
-                        vfree(tmp);
-                        for_each_online_cpu(j) {
-                                if (ucode_cpu_info[j].mc == tmp)
-                                        ucode_cpu_info[j].mc = NULL;
-                        }
+static int do_microcode_update (void)
+{
+        long cursor = 0;
+        int error = 0;
+        void * new_mc;
+        int cpu;
+        cpumask_t old;
+
+        old = current->cpus_allowed;
+
+        while ((cursor = get_next_ucode(&new_mc, cursor)) > 0) {
+                error = microcode_sanity_check(new_mc);
+                if (error)
+                        goto out;
+                /*
+                 * It's possible the data file has multiple matching ucode,
+                 * lets keep searching till the latest version
+                 */
+                for_each_online_cpu(cpu) {
+                        struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
+
+                        if (!uci->valid)
+                                continue;
+                        set_cpus_allowed(current, cpumask_of_cpu(cpu));
+                        error = get_maching_microcode(new_mc, cpu);
+                        if (error < 0)
+                                goto out;
+                        if (error == 1)
+                                apply_microcode(cpu);
                 }
-                if (ucode_cpu_info[i].err == MC_IGNORED && verbose)
-                        printk(KERN_WARNING "microcode: CPU%d not 'upgrading' to earlier revision"
-                               " 0x%x (current=0x%x)\n", i, ucode_cpu_info[i].cksum, ucode_cpu_info[i].rev);
+                vfree(new_mc);
         }
 out:
+        if (cursor > 0)
+                vfree(new_mc);
+        if (cursor < 0)
+                error = cursor;
+        set_cpus_allowed(current, old);
         return error;
 }
 
+static int microcode_open (struct inode *unused1, struct file *unused2)
+{
+        return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
+}
+
 static ssize_t microcode_write (struct file *file, const char __user *buf, size_t len, loff_t *ppos)
 {
         ssize_t ret;
@@ -470,6 +439,7 @@ static ssize_t microcode_write (struct file *file, const char __user *buf, size_
                 return -EINVAL;
         }
 
+        lock_cpu_hotplug();
         mutex_lock(&microcode_mutex);
 
         user_buffer = (void __user *) buf;
@@ -480,6 +450,7 @@ static ssize_t microcode_write (struct file *file, const char __user *buf, size_
                 ret = (ssize_t)len;
 
         mutex_unlock(&microcode_mutex);
+        unlock_cpu_hotplug();
 
         return ret;
 }
@@ -496,7 +467,7 @@ static struct miscdevice microcode_dev = {
         .fops           = &microcode_fops,
 };
 
-static int __init microcode_init (void)
+static int __init microcode_dev_init (void)
 {
         int error;
 
@@ -508,6 +479,28 @@ static int __init microcode_init (void)
                 return error;
         }
 
+        return 0;
+}
+
+static void __exit microcode_dev_exit (void)
+{
+        misc_deregister(&microcode_dev);
+}
+
+MODULE_ALIAS_MISCDEV(MICROCODE_MINOR);
+#else
+#define microcode_dev_init() 0
+#define microcode_dev_exit() do { } while(0)
+#endif
+
+static int __init microcode_init (void)
+{
+        int error;
+
+        error = microcode_dev_init();
+        if (error)
+                return error;
+
         printk(KERN_INFO 
                 "IA-32 Microcode Update Driver: v" MICROCODE_VERSION " <tigran@veritas.com>\n");
         return 0;
@@ -515,9 +508,8 @@ static int __init microcode_init (void)
 
 static void __exit microcode_exit (void)
 {
-        misc_deregister(&microcode_dev);
+        microcode_dev_exit();
 }
 
 module_init(microcode_init)
 module_exit(microcode_exit)
-MODULE_ALIAS_MISCDEV(MICROCODE_MINOR);